As railway ties become degraded after prolonged use, their condition deteriorates to the point where they need to be replaced because they are no longer able to function adequately. Conventional railway maintenance practice involves maintenance personnel walking the track periodically, inspecting the ties, and marking ties that are degraded to the point where they require replacement. Later, a tie train carrying replacement ties unloads groups of ties at various locations. A tie replacement crew then attempts to locate and remove the marked ties and replace them with the replacement ties.
This conventional practice has numerous shortcomings. The marks that are made to indicate ties that need replacement can wear off or wash off, or they can simply be overlooked by the tie gang even if they are not washed off. If the marks are washed off or overlooked, the ties may be unloaded at the wrong locations, so extra labor is required to move the ties an undue distance along the railway. Worse, defective ties may not be replaced because their markings are washed off or overlooked.
The personnel unloading the ties from the tie train must exercise judgment as to where to unload ties and how many to unload. It is not uncommon for there to be too few or too many replacement ties unloaded at a particular place. Also, it is common for the tie gang to have to move the ties over relatively long distances because the unloading location is too far away from the ties that require replacement. This can significantly increase the labor requirements and the time needed to replace the ties. It can also increase the need for the maintenance personnel to handle heavy ties that are coated with creosote or other chemicals that can create a health hazard.
If too many replacement ties are unloaded, the excess ties need to be picked up and loaded for transport to a place where they can be used. If too few replacement ties are unloaded, some of the ties that need to be replaced are not replaced due to the shortage of unloaded ties. Reporting of the number of ties that have been replaced is typically done by manual procedures that can be inaccurate. As a result, inventory management can suffer and the efficient scheduling of work is more difficult.